The present invention relates to an electrical device system including a battery pack, an electrical device, and a charging device. The present invention also relates to a battery pack.
Conventionally, a battery pack to supply electric power to an electrical device is provided with a current detecting unit that detects a battery current flowing from a battery in the battery pack to the electrical device during a discharge and from a charging device to the battery during a charge.
The current detecting unit is used for monitoring the battery current during the discharge from and the charge to the battery. The current detecting unit includes, for example, a current detecting element (current detection resistor, in general) provided in a conduction path to the battery, and a detection circuit that detects the battery current via the current detecting element.
In the current detecting unit, an abnormal current flowing to the battery and the peripheral circuit cannot be detected if the detection circuit fails. Thus, it is no longer possible to protect the electrical device system from an excess current and the like.
For example, in Japanese Patent Application Publication No. 2012-90368, it has been proposed providing two ICs, that is, a charge and discharge control IC (microcomputer) and a battery voltage monitoring IC, with a function as a detection circuit that detects a battery current via a current detecting element, to determine whether or not the current detecting unit is operating normally, based on a difference in the battery currents acquired from the two ICs.